Sulfur and Fluorine Containing Anode Gases Produced during Normal Electrolysis and Approaching an Anode Effect

Dorreen, Mark; Chin, Darrell L.; Lee, Jackie K. C.; Hyland, Margaret; Welch, B. J.

doi:10.1007/978-3-319-48156-2_135

Cited by 9 publications

(11 citation statements)

References 6 publications

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“…The formation of COF 2 and C 3 F 6 during anode effect have also been reported [3,8]. COF 2 is unstable and decomposes (2 COF 2 + C = 2 CO + CF 4 ).…”

Section: The Effect Of Local Alumina Depletionmentioning

confidence: 63%

“…The PFC emission has for a long time been a concern of the aluminium industry, and considerable efforts have been spent on this problem [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. However, one should be aware of "similar" electrolytic processes that apply carbon anodes in fluoride melts may have related problems.…”

Section: Low Voltage Non-propagating Aementioning

confidence: 99%

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Low Voltage PFC Emission from Aluminium Cells

Thonstad¹,

Rolseth²,

Тонстэд³

et al. 2017

J. Sib. Fed. Univ. Chem.

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It is well known that the perfluorocarbon (PFC) gases CF 4 and C 2 F 6 are being emitted during anode effects in aluminium cells. These PFC compounds are very strong greenhouse gases, and the aluminium industry has made great efforts to reduce these emissions. From 1990 to 2008 a 90% reduction in PFC emissions has been achieved. However, during the last few years we have received new alarming information, mainly from the Chinese aluminium industry, that there is an almost continuous emission of PFC gases from aluminium potlines even in the absence of anode effects, and it accounts for 10 to 90%of the total PFC emissions, the median being 70%. They named it "Non-anode effect PFC emissions". This information has later been confirmed from several sources, so it seems to be a universal problem. Ключевые слова: алюминиевый электролизер, анодный эффект, перфторулероды (ПФУ). IntroductionDuring the last 20 years strong efforts have been made in order to reduce the emission of PFC (perfluorocarbon) gases from the aluminium industry. These gases are being emitted during the so-called anode effect, which occurs when the concentration of dissolved alumina in the bath gets too low (< 0.5-2 wt%). The cell voltage then rises abruptly to 15-40 V, and an anode effect is on [1]. In order to extinguish anode effects, alumina is being fed, and the bath is being agitated in various ways, e.g. by inserting wooden poles or by repeatedly raising and lowering the anode beam.The PFC emissions from any given plant are being reported to the national environmental protection agency. It is being calculated by taking the time on anode effect multiplying it by an empirical factor, named "the slope". The units are ton CO 2 eq./ton Al. The time on anode effect is normally recorded as the time -32 -Jomar Thonstad and Sverre Rolseth. Low Voltage PFC Emission from Aluminium Cells above 8 V cell voltage. This data is being recorded due to the fact that the PFC gases, CF 4 and C 2 F 6 , are very potent greenhouse gases, contributing to global warming. CF 4 is 6500 times and C 2 F 6 is 9200 times stronger greenhouse gases than CO 2 . The initiative for this reporting comes from "The United Nations Intergovernmental Panel on Climate Change" (IPCC), and the data are being collected and reported by the International Aluminium Institute (IAI) in London. IAI has reported that the average PFC emissions have been reduced from close to 5 ton CO 2 eq./ton Al in 1990 down to 0.70 in 2010, and a goal of 0.34 in set for [2].This remarkable achievement is the result of impressive efforts made by the aluminium industry over the years by introducing new technology and improved cell control and cell operation. This is really a success story. But is it the whole story?Apparently it is not the whole story. In recent years there have been several reports [2][3][4][5] showing that under certain circumstances, PFC emissions are also being detected during normal operation when there is noongoing anode effect in thepotline. It has been named "non-anode effect PFC emission...

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“…The formation of COF 2 and C 3 F 6 during anode effect have also been reported [3,8]. COF 2 is unstable and decomposes (2 COF 2 + C = 2 CO + CF 4 ).…”

Section: The Effect Of Local Alumina Depletionmentioning

confidence: 63%

Section: Low Voltage Non-propagating Aementioning

confidence: 99%

Low Voltage PFC Emission from Aluminium Cells

Thonstad¹,

Rolseth²,

Тонстэд³

et al. 2017

J. Sib. Fed. Univ. Chem.

View full text Add to dashboard Cite

show abstract

“…While formation of COF 2 is favourable thermodynamically, this species has only been reported once in laboratory-scale experiments with inert gas. 52 An attempt to reproduce this experiment was not successful. 71 It has been suggested that COF 2 is unstable and will either react with carbon to form PFC's 52 or self-disproportionate to form CF 4 and CO 2 .…”

Section: Fluoridesmentioning

confidence: 99%

“…Experimental data clearly show that COS is the dominating sulfurous gas species when oxidation is avoided. 48,49,52,54,55 Although the gas species H 2 S and CS 2 are frequently reported in small amounts in the anode gas, it is only occasionally reported for duct gas measurements. Most likely the observed CS 2 (and H 2 S) is a result of decomposition of COS at intermediate temperatures (350-600°C).…”

Section: Sulfurous Gas Speciesmentioning

confidence: 99%

“…It is speculated whether SO 3 adsorption onto particulates can effectively lower the SO 3 concentration in the gas phase. 52 One likely option is that SO 2 is adsorbed on particulates where it is converted to SO 3 , which reacts to sulphates. The observation of sulphates in the particulates from the off-gas 8,9 suggests an interaction between gaseous sulfur species and the particulates.…”

Section: Sulfurous Gas Speciesmentioning

confidence: 99%

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